Development of a Prototypical Historic Fire Risk Index to Evaluate Fire Safety in Historic Buildings (1998-08)

The difficulty of imposing building and fire codes on historic buildings has been a subject of wide spread concern in recent decades. Most such codes are prescriptive, specification based criteria that rigidly dictate how a building should be constructed or rehabilitated. They are oriented to new buildings, anticipating modem construction materials and assemblies. When applied to historic buildings such code requirements are often impractical or damaging to architectural and historic character.

Fire risk indexing is a more flexible and inclusive technique for evaluating alternative fire safety configurations in buildings. A fire risk index is a tabular tool for analyzing and scoring hazards and other risk parameters that describe various building features or systems related to fire safety. Numerical values assigned to these parameters are arithmetically manipulated to create a single mathematical expression for the overall level of fire safety provided by the building. Like the codes, existing fire risk index systems focus on modern construction techniques. While these indexing systems can be useful tools for rehabilitation projects, they do not include the range of alternatives that are appropriate for buildings of historic significance.

This project, funded by NCPTT, has produced a prototype fire risk index specifically for historic house museums. An historic house museum is defined as a structure with recognized historic designation, or apparent historic significance, that is open to the public to display the building and its contents. Most often, the historic house museum was originally designed as a single family home. It is typically managed by professional or qualified staff or volunteers with specific expertise in museum management or historic preservation. To a significant extent, the fire risk is dictated by its relatively small size and characteristic function.

The Historic Fire Risk Index (HFRI) is based on two existing risk indexes that have established empirical validity. From these systems, a combined set of fire safety parameters was mathematically normalized and ranked according to their intrinsic level of significance. The parameter list was then adapted for application to historic house museums. This process had four stages: (1) some parameters were identified as not applicable to historic house museums and were deleted from the list, (2) some parameters were combined to better represent their effectiveness, (3) some parameters were expanded to amplify their importance, and (4) new parameters were added to cover the range of fire risk in historic house museums. This latter is the most significant as it introduces fire prevention, emergency response, and historic significance, areas not explicitly addressed by building codes.

The resulting list of eleven fire risk parameters is the essence of the HFRI. Associated with each parameter is a weight or measure of importance derived from the existing fire risk index systems. Onsite survey of an individual historic house museum determines the presence of physical factors that influence effectiveness of the parameters. From this information, a numerical grade for each parameter is calculated by reference to prescribed algorithms created in this research or adapted from existing fire risk index systems. A total fire safety score is computed as the weighted sum of the parameter weights and grades. This score may be compared with an alternative configuration of parameters within a specific historic house museum or to different facility. The result is a relative comparison of fire risk that allows more flexibility than existing building and fire codes. Preliminary field testing has established the HFRI as a workable prototype and identified areas for future improvement.